As COVID breakthrough infections rise, should vaccinated people worry?

Breakthrough COVID-19 infections — when fully inoculated people get the virus — were expected following the rollout of vaccines.

Surgeon General Vivek Murthy shared on ABC’s “This Week on Sunday,” “Even if you do have a breakthrough infection, it's much more likely that that infection will be either asymptomatic or mild. And that's really good news that continues to tell us that these vaccines are highly effective and that's one of the reasons we are recommending them.”

And yet, breakthrough cases are rising and U.S. Olympic athletes have tested positive, like gymnast Kara Eaker and basketball player Katie Lou Samuelson.

Tracking breakthrough infections is critical to understanding how and why they’re happening, and whether treatments are working, says Katherine Wu, who covers science for the Atlantic.